The present invention relates to a pedal device having a damper for imparting an appropriate brake to an accelerator pedal arm, a brake pedal arm, a clutch pedal arm, or the like of an automobile and a damper suitable for use in the pedal device.
Fine control of fuel injection in automotive engines is required for the purposes of low fuel consumption of automobiles and reduction of carbon dioxide, and electronic regulation of the throttle valve opening based on the pressing down of an accelerator pedal has been put to practical use.
In automobiles in which fuel injection of the engine is effected by electronic control, an accelerator cable disposed between an accelerator pedal arm and a throttle valve is normally omitted. With these automobiles without the accelerator cables, the feeling of reaction force with respect to the pedal pressing force differs in comparison with the accelerator cables. Moreover, the hysteresis characteristic in the relationship between the pressing force in the pedal pressing direction and the holding force in the pedal returning direction forms a substantially narrow loop, i.e., the pedal-pressing-force characteristic with respect to the amount of the pedal pressed becomes linear. Therefore, if a general driver who is accustomed to driving an automobile with the accelerator cable drives the automobile without the accelerator cable, there arises a problem in that, for instance, fatigue can occur early when shocks of the acceleration or deceleration of the automobile occur due to the movement of the accelerator pedal during running on a rough terrain, or when the driver tries to fixedly hold the accelerator pedal for a long time during such as high-speed running.
To prevent excessive pressing down by obtaining a large reaction force with respect to the pedal pressing force, if the spring force of a return spring for returning the pedal arm to the initial position of rotation is simply made large, there is a possibility of causing early fatigue to the pedal-pressing foot due to the large reaction force from the return spring during constant-speed running.
Accordingly, a damper has been proposed which imparts a resistance force based on linearly increasing friction between a rotating member rotated by the rotation of the pedal arm and a movable member coming into contact with this rotating member. According to this damper, it is possible to obtain favorable effects such as that the damper has such a hysteresis characteristic that the range of the pedal pressing force allowing the amount of the pedal pressed to be maintained at a fixed level in correspondence with the amount of the pedal pressed can be made large, that the damper can be installed compactly, that the adjustment of the reaction force can be effected very simply, and that a change in its characteristics can be reduced. However, since the hysteresis characteristic is obtained on the basis of dynamic friction and static friction, large resistance based on static friction before leading to dynamic friction is applied to the pedal arm as a reaction force at the start of the pressing down of the pedal from the initial position of rotation of the pedal arm. Consequently, the driver of the automobile who operates the pedal arm receives from the pedal the unpleasant sensation of, as it were, pressing the foot against an immovable wall in the early stage of pressing down, and thus experiences a feeling of fatigue in the pedal operation.
The above-described problem occurs not only with the accelerator pedal arm, but can also occur with, for example, the brake pedal arm, the clutch pedal arm, and the foot-operated parking brake arm.
The present invention has been devised in view of the above-described aspects, and its object is to provide a pedal device for an automobile which excels in the operational feeling, does not cause the driver to experiences a feeling of fatigue in the pedal operation, and makes it possible to enlarge the range of the pedal pressing force allowing the amount of the pedal pressed to be maintained at a fixed level in correspondence with the amount of the pedal pressed, as well as a damper suitable for use in the pedal device.
A pedal device for an automobile in accordance with a first aspect of the invention comprises a damper for imparting a resistance force to the rotation of a pedal arm, the damper including a movable member which is disposed movably in an axial direction but immovable in a direction about the axis, a rotating member disposed rotatably about the axis and facing the movable member, spring means for resiliently urging the movable member toward the rotating member, and frictional-resistance-force generating means for producing a frictional resistance force as the resistance force in the rotation of the rotating member, and for increasing the frictional resistance force by increasing the spring force of the spring means by causing the movable member to move away from the rotating member in the axial direction against the resiliency of the spring means, wherein a torque which gradually increases from an initial position of rotation of the pedal arm to any angle of 0.5 to 20% of a full angle of rotation thereof is imparted to the rotating member to permit the rotation of the pedal arm, and the rotating member is subsequently rotated in conjunction with the rotation of the pedal arm.
In accordance with the pedal device according to the first aspect, a torque which gradually increases from the initial position of rotation to any angle of 0.5 to 20% of the full angle of rotation is imparted to the rotating member to permit the rotation of the pedal arm, and the rotating member is subsequently rotated in conjunction with the rotation of the pedal arm. Accordingly, at the start of the pressing down of the pedal, the pedal arm is rotated in conjunction with it, with the result that it is possible to eliminate the sensation of being subjected to a large resistance based on the static friction in the frictional-resistance-force generating means. Hence, the driver who operates the pedal arm is able to start the automobile naturally without receiving from the pedal the unpleasant sensation of pressing the foot against, so to speak, an immovable wall, and is able to comfortably effect the pedal operation without experiencing fatigue.
If the angle of rotation of the pedal arm for rotating the rotating member in conjunction with the rotation of the pedal arm is less than 0.5% of the full angle of rotation, the driver receives a large reaction force based on the static friction in the frictional-resistance-force generating means substantially at the same time as the pressing of the pedal. This situation is substantially similar to the case in which the foot is pressed against an immovable wall, and natural starting of the automobile is hence impossible. On the other hand, the angle of rotation of the pedal arm exceeds 20% of the full angle of rotation, the range of the pedal pressing force allowing the amount of the pedal pressed to be maintained at a fixed level in correspondence with the amount of the pedal pressed (the angle of rotation of the pedal arm) becomes small, and this effect can be obtained only at a high speed.
In addition, in accordance with the pedal device according to the first aspect, when the rotating member is rotated by the rotation of the pedal arm due to the pressing down of the pedal, the frictional resistance force which increases occurs in the frictional-resistance-force generating means. Therefore, by virtue of this resistance force, it is possible to prevent fuel from being consumed more than before by, for example, excessively pressing down on the accelerator pedal. Moreover, as the result of the fact that it is possible to enlarge the range of the pedal pressing force in which the angle of rotation of the pedal arm can be maintained at a fixed level in correspondence with the amount of the pedal pressed, the amount of the pedal pressed can be easily maintained at a fixed level in correspondence with the speed during the constant-speed running at various speeds ranging from the low speed to the high speed. Hence it is possible to overcome the trouble of such as causing early fatigue to the pedal-pressing foot.
In the pedal device for an automobile in accordance with a second aspect of the invention, in the pedal device according to the first aspect, the frictional-resistance-force generating means has an inclined surface formed on one surface of the rotating member facing the movable member and an inclined surface formed on one surface of the movable member facing the rotating member and adapted to be brought into planar contact with the inclined surface.
In accordance with the pedal device according to the second aspect, by appropriately setting the coefficients of friction of both inclined surfaces, it is possible to approximately determine the resistance force which can be applied to the rotation of the pedal arm. Further, it is possible to effect very simply the adjustment of the reaction force having a hysteresis characteristic in the relationship between the amount of the pedal pressed and the pedal pressing force.
In the pedal device for an automobile in accordance with a third aspect of the invention, in the pedal device according to the first or second aspect, the movable member has a movable member body and a projection formed integrally on one surface of the movable member body in such a manner as to project in the axial direction toward one surface of the rotating member, the rotating member has a rotating member body and a projection formed integrally on one surface of the rotating member body in such a manner as to project in the axial direction toward the one surface of the movable member, and the frictional-resistance-force generating means has inclined surfaces which are formed on both projections of the movable member and the rotating member and are brought into planar contact with each other.
In the pedal device according to the third aspect, since the the frictional-resistance-force generating means is formed by inclined surfaces which are formed on both projections of the movable member and the rotating member and are brought into planar contact with each other, the pedal device can be made very compact, and can be installed by making effective use of a small space. Furthermore, by appropriately setting the coefficients of friction of the inclined surfaces which are brought into planar contact with each other, it is possible to approximately determine the resistance force which can be applied to the rotation of the pedal arm. Further, it is possible to effect very simply the adjustment of the reaction force having a hysteresis characteristic in the relationship between the amount of the pedal pressed and the pedal pressing force.
In the pedal device for an automobile in accordance with a fourth aspect of the invention, in the pedal device according to any one of the above-described aspects, the rotation of the pedal arm is adapted to be transmitted to the rotating member via a rotatable shaft, the damper further includes a hollow cylindrical member in which the movable member and the rotating member are accommodated and a cover disposed at one end surface of the hollow cylindrical member in such a manner as to be immovable in the direction about the axis, the rotating member is in contact with the cover in such a manner as to be slidable in the direction about the axis and by being urged by the spring force of the spring means, and the movable member is in contact with the hollow cylindrical member in such a manner as to be slidable in the axial direction.
In the pedal device according to the fourth aspect, in the rotation of the rotating member, the frictional resistance between the rotating member and the cover and the frictional resistance between the movable member and the hollow cylindrical member can be respectively added to the frictional resistance of the frictional-resistance-force generating means. Therefore, the frictional-resistance-force generating means can be arranged more compactly.
In the pedal device for an automobile in accordance with a fifth aspect of the invention, in the pedal device according to the fourth aspect, the pedal arm and the rotatable shaft are substantially rigid members in comparison with the hollow cylindrical member, the rotating member, the movable member and the cover, and the rotation of the pedal arm from the initial position of rotation to any angle of 0.5 to 20% of the full angle of rotation is effected by the elastic deformation of at least one of the hollow cylindrical member, the rotating member and the movable member.
In accordance with the pedal device according to the fifth aspect, since the early rotation of the pedal arm is allowed by the elastic deformation of at least one of the hollow cylindrical member, the rotating member and the movable member, a resilient reaction force is gradually applied to the pressing foot in proportion to the amount of pressing, so that the operational feeling during the early rotation of the pedal arm can be made very excellent.
In the case where the early rotation of the pedal arm is effected by the elastic deformation of the hollow cylindrical member, the rotating member and the movable member, by appropriately setting their moduli of elasticity, it is possible to provide a pedal device imparting an optimum operational feeling in the early rotation of the pedal arm.
As the materials for forming the hollow cylindrical member, the rotating member and the movable member for effecting the elastic deformation, the following are required. First, since a rotatable shaft is normally inserted in the rotating member, and this rotatable shaft repeats rotational motion, the rotating member must be such as to be able to withstand its repeated stress, and breakage and permanent set in fatigue (permanent deformation) must not occur. Moreover, since the rotating member slides on the movable member, and on the cover in some cases, the rotating member should preferably be formed of a material which excels in wear resistance and generates a stable frictional torque. In a case where the rotatable shaft is directly inserted in the rotating member, a fairly high strength is required for the rotating member, but by interposing a link mechanism or the like without directly inserting the rotatable shaft, it is possible to reduce the load applied to the rotating member.
As for the movable member and the hollow cylindrical member, the strength is not so much required as the rotating member, but, basically speaking, the breakage and the permanent set in fatigue must not occur in the repeated rotation of the rotating member in the same way as the rotating member, and the movable member and the hollow cylindrical member should preferably be formed of materials which excel in wear resistance and generate a stable frictional torque in sliding with their respective mating members.
By taking these aspects into consideration, it suffices if a modulus of elasticity in bending, E, of a material for forming the hollow cylindrical member is such that 2xc3x97104 kgf/cm2xe2x89xa6E as in the pedal device in accordance with a sixth aspect of the invention. In addition, the material for forming the hollow cylindrical member should preferably be formed of a resin as a base material as in the pedal device in accordance with a seventh aspect of the invention. Such a resin is not particularly restricted insofar as a required modulus of elasticity in bending is satisfied in the relationship with the movable member and the rotating member and in the relationship with the pedal device according to the sixth aspect of the invention, and it is possible to use a resin as a simple substance or a combination of two or more kinds of resins, or a material in which various fillers are compounded with these resins. Preferably, as in the pedal device in accordance with an eighth aspect of the invention, as the resin, the material for forming the hollow cylindrical member is one kind or two or more kinds selected from a polyamide resin such as nylon 6, nylon 66, nylon 12, nylon 46 or nylon MXD6, a polyoxymethylene resin such as an acetal copolymer or an acetal homopolymer, a thermoplastic polyester resin such as polyethylene terephthalate or polybutylene terephthalate, a liquid crystal polyester resin, a modified polyphenylene ether resin, a polyphenylene sulfide resin, a polyether sulfone resin, an aliphatic polyketone resin and a polyether ketone resin. Further, as in the pedal device in accordance with a ninth aspect of the invention, the filler includes one kind or two or more kinds selected from graphite, fluororesin, molybdenum disulfide, boron nitride, glass fibers, carbon fibers, aromatic polyamide fibers and potassium titanate whiskers, as well as lead, zinc, tin and copper and alloys thereof. It should be noted that, depending on a case, the material for forming the hollow cylindrical member may be a metal which can be regarded as a substantially rigid material as in the pedal device in accordance with a 10th aspect of the invention.
The modulus of elasticity in bending, E, of a material for forming the movable member is such that 2xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa620xc3x97104 kgf/cm2 as in the pedal device in accordance with an 11th aspect of the invention, preferably 5xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa620xc3x97104 kgf/cm2 as in the pedal device in accordance with a 12th aspect of the invention, more preferably 7xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa618xc3x97104 kgf/cm2 as in the pedal device in accordance with a 13th aspect of the invention. The modulus of elasticity in bending, E, of a material for forming the rotating member is such that 2.5xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa625xc3x97104 kgf/cm2 as in the pedal device in accordance with a 14th aspect of the invention, preferably 5xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa623xc3x97104 kgf/cm2 as in the pedal device in accordance with a 15th aspect of the invention, more preferably 10xc3x97104 kgf/cm2xe2x89xa6Exe2x89xa620xc3x97104 kgf/cm2 as in the pedal device in accordance with a 16th aspect of the invention.
It should be noted that if the modulus of elasticity in bending, E, of the material for forming the rotating member exceeds 25xc3x97104 kgf/cm2, it is necessary to make substantially small the moduli of elasticity in bending, E, of the materials for forming the movable member and the hollow cylindrical member, and there are possibilities of causing breakage and permanent set in fatigue, thereby causing a problem in durability.
In the case where the early rotation of the pedal arm is effected by the elastic deformation of the hollow cylindrical member, the rotating member and the movable member, the respective materials of the movable member and the rotating member can be appropriately selected from materials which satisfy the aforementioned moduli of elasticity in bending. The combination of the materials, however, may be determined by taking into consideration the hysteresis characteristic and the sliding characteristic that are required.
The materials for forming the movable member and the rotating member should preferably comprise resins in the same way as the material for forming the hollow cylindrical member, as in the pedal device in accordance with a 17th aspect of the invention. In this case, the resins for forming the movable member and the rotating member are not particularly restricted insofar as the required modulus of elasticity in bending is satisfied in the relationship with the hollow cylindrical member. In the same way as the material for forming the hollow cylindrical member, it is possible to use a resin as a simple substance or a combination of two or more kinds of resins, or a material in which various fillers are compounded with these resins.
As in the pedal device in accordance with an 18th aspect of the invention, as the resins, each of the materials for forming the movable member and the rotating member preferably comprises one kind or two or more kinds selected from a polyamide resin such as nylon 6, nylon 66, nylon 12, nylon 46 or nylon MXD6, a polyoxymethylene resin such as an acetal copolymer or an acetal homopolymer, a thermoplastic polyester resin such as polyethylene terephthalate or polybutylene terephthalate, a liquid crystal polyester resin, a modified polyphenylene ether resin, a polyphenylene sulfide resin, a polyether sulfone resin, an aliphatic polyketone resin and a polyether ketone resin. Further, as in the pedal device in accordance with a 19th aspect of the invention, the filler which is compounded therewith preferably includes one kind or two or more kinds selected from graphite, fluororesin, molybdenum disulfide, boron nitride, glass fibers, carbon fibers, aromatic polyamide fibers and potassium titanate whiskers, as well as lead, zinc, tin and copper and alloys thereof.
It should be noted that the pedal arm in the device of the invention is preferably the aforementioned accelerator pedal arm, but, alternatively, the pedal arm is also applicable to a brake pedal arm, a clutch pedal arm, or the like.
Hereafter, a description will be given of the present invention and its embodiment with reference to the preferred example shown in the drawings. It should be noted that the present invention is not limited to this embodiment.